# Chapter 1, Equations and Graphs - Section 1.6 - Solving Other Types of Equations - 1.6 Exercises - Page 139: 75

$x=\pm\sqrt{a}$ or $x=\pm2\sqrt{a}$

#### Work Step by Step

$x^{4}-5ax^{2}+4a^{2}=0$ $(a-x^{2})(4a-x^{2})=0$ $a-x^2=0$ or $4a-x^2=0$ $x=\pm\sqrt{a}$ or $x=\pm2\sqrt{a}$ (We can take the square root of $a$ because it is positive.)

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